1. Technical Field
This disclosure relates to an image forming apparatus, and more specifically to an image forming apparatus including a moving assembly of a recording head having droplet ejection nozzles and a maintenance device.
2. Description of the Related Art
Image forming apparatuses are used as printers, facsimile machines, copiers, plotters, or multi-functional devices having two or more of the foregoing capabilities. Such image forming apparatuses may use a droplet ejection device having a recording head (droplet ejection head) to eject droplets of ink or other liquid.
Such a droplet-ejection type of image forming apparatus typically, while conveying a recording medium (e.g., a recording sheet of paper), ejects liquid droplets from a recording head and attaches or penetrates the droplets on the recording medium for image formation. The recording medium (target) is not limited to the above-described recording sheet of paper but is made of string, fiber, leather, metal, resin, glass, timber, ceramic, or any other material on which liquid is attachable or penetrable.
The droplet ejection device performs maintenance and recovery operation (hereinafter, maintenance operation) to prevent faulty ejection of liquid from nozzles of the recording head. The maintenance operation is a process of preventing an increase in the viscosity of ink or other liquid due to natural drying and removing viscosity-increased and firmly adhered liquid by sucking operation to maintain and recover performance of the recording head, and a maintenance and recovery device (hereinafter, maintenance device) is used to perform the maintenance operation.
The maintenance device includes a cap member to seal a nozzle face of the recording head to maintain a humid state, a wiper member to wipe the nozzle face, and a suction pump connected to the cap member. The maintenance device performs cleaning operation to create a negative pressure by the suction pump with the nozzle face sealed with the cap member to forcefully discharge bubbles or viscosity-increased liquid from nozzles of the recording head.
During not only the maintenance operation but also a standby period of the recording head, the cap member seals the nozzle face of the recording head to maintain a humid state of the nozzles, thus minimizing drying of liquid and an increase in the viscosity of liquid.
As a configuration of the maintenance device, for example, JP-2007-223227-A proposes to provide cap and other members detachably attachable relative to nozzle faces of recording heads. For example, in a case in which liquid droplets are ejected from the recording heads in a vertical direction, the cap members are elevated up and down relative to the nozzle faces of the recording heads facing down. For such a configuration, an elevation start position of a cam of an elevation driving unit is set by determining a rotation start position, i.e., a home position of a cam shaft so that a rising stroke for appropriate contact between a nozzle face of a recording head and the cap and other members can be obtained when the cam is raised from the elevation start position.
In addition, as a configuration of defining an opposing position at which, when raised, a cap member opposes a nozzle face of a recording head, for example, JP-4233984-B (JP-2005-144912-A) proposes to engage an engagement claw of a cap member with an engagement portion of a nozzle face of a recording head to define the opposing position.
If cap and other members oppose a nozzle face of a recording head at a position differing from a predetermined opposing position and are raised in response to a rotation of a cam shaft to detect a home position of the cam shaft, a portion of the cap and other members might contact the nozzle face of the recording head. In particular, if a carriage mounting the recording head is moved when the cap and other members are not placed at a predetermined position, for example, an engagement claw of the cap member might contact the nozzle face of the recording head, thus damaging nozzles or menisci of nozzles.